Update: I completed the treadmill motor upgrade. It seems to work awesome!
100 RPM to 1850 RPM so I lost a little top end but am able to slow things down a bit more.
I still have 3 stages of the belt pulley too, so if I really need the top end I can up the gearing a stage and get in excess of 2500 RPM. (or around 3800 if I go to the highest belt.)
I haven't actually turned with it yet, just got the controller tuned up. I had to adjust the Max pot a bit, it was 0nly getting to 78V with the factory trim.
I also bumped IR which seemed to help low end torque... I can barely stall it by hand at 100 RPM.
I'll post more when I get a chance to do some real work on it. I think my next project will be a new tool post hold down nut and spacer for the base... to try and stiffen up the A2Z CNC toolpost some.